Process for the purification of raw water from colloidal humic substances



April 8- A. M. R. KARLSTROM 7 2,449,514

PROCESS FOR THE PURIFICATION OF" RAW WATER FIIOM COLLOIDAL HUMIC SU Filed Nov. 16, 1944 INVENTOR.

fldqz m Karla-Tr m /h/ZM- ATTORNEY.

Bs-rmcss Patented Apr. 2' 7, 1948 2,440,514 PROCESS FOR THE PURIFICATION OF RAW WATER M COLLOIDAL HUMIC SUB- STAN CES Adolf Magnus Rupert Karlstrom,

- Goteborg, Sweden Application November 16,

In Sweden November 23, 1943 2 Claims. (Cl. 210-16) The present invention relates to processes for the purification or raw water. For the purification of'such water it' is customary to add suitable quantities of alum and alkali to the raw water whereby the humic substances will be coagulated. The addition of said chemicals takes place continuously and, as a rule, while subjecting the water to a slow agitation. The water then flows through large basins where most part of the flocs, which incessantly increase in size, deposits. The water with small humic flocs flowing through the sedimentation basins is passed to sand filters where the remaining humlc flocs are to be retained. The drawbacks of such a purification plant are great capital and working costs, large space required and discontinuity in its operation.

According to the present invention the humic substances are separated from the raw water by flotation, since the humic substances have been flocculated by the addition of a water soluble'salt with a trivalent positive ion such. as aluminium, iron and chromium, and air has been introduced into the water whereby the latter obtains the quantity of air required for the flotation as well as is thoroughly agitated which promotes the flocculation of the 'colloidal humic substances. For it is a known fact-that a thorough agitation of the water promotes the flocculation of colloidal substances. By the aeration of the water and the escape of the air superfluous for the flotation proper before the entrance of the water into the flotation tank each portion of the. water mass will be subjected to an eflicient agitation. The flotation may be carried out under outer atmospheric pressure or under reduced pressure. In both cases the water flows in an upwardly directed current and consequently through a preferably vertical conduit into the flotation tank. In this upward flow the water is subjected to an agitation by an agitator. If the raw water has obtained the suitable preparatory treatment the humic substances flocculated may be separated by flotation in a very satisfactory manner. In opposition to sedimentation and filtration this flotation ofiers the advantage of a complete continuity in its manner of operation and it may be carried out by an apparatus requiring small space and to relatively low costs.

After the aeration of the raw water and the flocculation of the humic substances by the addition of a water soluble salt with a trivalent positive ion, small quantities of a colloid with negative charge, such as animal glue or other albumin, resin glue completely saponifled, soap solution, sulphonated aliphatic and resin acids may be 1944, Serial n 563,711

another salt with trivalent positive ion is sup-' plied through the inlet pipe 4 to the nozzle of the ejector whereby the first admixture of the alum solution is' attained. The water aerated and mixed with alum enters into the open box or vessel 5 where a great part of the superfluous air disturbing for the subsequent treatment escapes. From the box 5 the water passes through. the conduit 1 to a flocculation tank 8 into which the conduit 71 enters tangentially. If alkali be used in connection with the flocculation it is added at 6. If desired, alum and alkali may be added at 9 and 50 respectively. In the tank 8 the water is subjected to a slow agitation by means of the agitator ii whereby the humic substances are I separated as flocs. The water intermingled with flocs escapes through flutes l2 disposed under the water level in the tank 8 to the catch chamber is and from the latter through the conduit l! to the ascending tube B5 of the flotation tank. Also into the-ascending tube the water'enters tangentially.

Above all in the box 5 but'also in the tank 8 air bubbles detrimental to the flotation will I escape, and these air bubbles produce movements of the water so that an intimate mixture of the water and alum solution takes place.

In the use of a negatively charged colloid the addition thereof takes place in the flow of water between i3 and I l. The purpose of this addition is to bind the small humic flocs together, to stabilize the flocs and to make the same more suitable for the retaining of the air bubbles.

In the ascending tube I 5 the water is sub- Jected to a further slow agitation by means oi. the agitator l8 whereby the size of the flock will be increased still more. In the flow oi the water up to the flotation tank I], in which a reduced pressure corresponding to a water column 01' about 2.5 to 3 meters is maintained, the air dissolved in the water is separated in the form Of small air bubbles on the humic flocs whereby these flocs are raised to the water level in the tank. By means of scrapers and a rotary suction nozzle 18 the docs raised to the level are removed from the tank while purified water free from flees escapes through a plurality oi! discharge openings is to an annular channel 20 at the bottom of the tank II. From this channel the water is. discharged through a system or discharge tubes 2| which are connected to a discharge tube 22 extending down into a vessel 23 serving as water trap. This vessel 21 is adapted to be elevated or-lowered. 24 indicates a conduit tor the filling oi the flotation tank II in connection with the starting of the apparatus, and 26 a water conduit used in connection with cleansing oi. the tank I7 and the nozzle 19.

What I claim is:

1. A process for the purification of raw water from colloidal humic substances, comprising, in combination, introduction air into the water, addition of water soluble salt with trivalent positive ion of oneof the metals aluminium, iron and chromium, subsequent slow agitation of the water for the coagulation of the humic substances, and separation by flotation of the coagulated humic substances from the water.

2. A process for the purification of raw water from colloidal humic substances, comprising, in combination, aeration of the water, addition 01 water soluble salt with trivalent positive ion of one of the metals aluminium, iron and chromium, subsequent slow agitation of the water for the coagulation of the humic substances, then addiwater.

ADOLF MAGNUB RUPERT KARLS'I'ROM.

0E8 CITED The following references are of record in the o tile oi this patent:

UNITED STATES PATENTS Number Name Date French June 24, 19,13 Ripley Dec. 29, 1914 Edser Mar. 9, 1920 Fender Nov. 23, 1926 Ravnestad Mar. 1, 1927 Simpson June 14, 1927 Alsberg June 13, 1929 ,Borrowman Aug. 17, 1937 Krchma Mar. 22, 1938 Anderson Aug. 9, 1938 Velz Aug.30, 1938 McCord Oct. 11, 1938 Karlstrom July 8, 1941 Tolman Dec. 1-6, 1941 Daily June 1, 1943 Kelly et a1 July 13, 1943 Clemens May 8, 1945 Lawlor Aug. 14, 1945 

